The present invention relates to a process for the manufacture of salts of hydroxycarboxylated polymers of reduced molecular weight. The products thus obtained can be used as active adjuvants (sequestering agent or "builder") in detergent compositions.
Processes are known for the depolymerization in solution of polymers such as polyethylene and polypropylene, using oxidizing agents. See British Pat. No. 883,804. These processes have the disadvantages that they are accompanied by a degradative oxidation of all or part of the polymer, which leads to the formation of colored products and necessitates subsequent bleaching treatments, and that they produce inconvenient byproducts arising from the oxidation of the solvent.
In the manufacture of salts of non-hydroxylic carboxylic acid polymers of reduced molecular weight, it is known to neutralize the corresponding polycarboxylic acid which already has a low molecular weight. See U.S. Pat. No. 3,637,609 which concerns the fabrication of sodium polymaleate by neutralization of polymaleic acid.
These processes result in large losses of products. In addition, they require numerous reaction steps. Finally, they do not generally make it possible to obtain perfectly white products without a subsequent bleaching operation. Thus, in U.S. Pat. No. 3,637,609, the sodium polymaleate salt obtained by the neutralization is in the form of finely divided pale yellow particles which are then bleached with a bleaching agent such as hydrogen peroxide, peracetic acid, sodium hypochlorite, perbenzoic acid or ozone.